Under-ice Biota at the Pond Inlet Ice Edge and in Adjacent Fast Ice Areas during Spring

Abstract

Distributions of nutrients, flora and fauna on the bottom of the ice in Pond Inlet during May-July 1979 were examined with respect to distance from the landfast ice edge, but temporal variability and local spatial variability confounded interpretation. Timing of the ice algal bloom was most delayed under fast ice where snow depth was thickest and was negatively correlated with chlorophyll a content in bottom ice. The bloom occurred first at the ice edge where snow and ice thickness were least and were positively correlated with ice chlorophyll. Standing stocks of ice microalgae at each station were dominated by pennate diatoms, especially Nitzschia grunowii and N. frigida, and were not closely related to distance from the ice edge. High densities of nematodes and harpacticoid and cyclopoid copepodites in the bottom layer of ice were associated with high densities of microalgae, and maximum meiofaunal densities (approx. 50,000 individuals per square m) occurred in masses of algae sloughing off the ice. Macrofaunal communities on the under-ice surface included 9 amphipod and 1 mysid species, and were dominated by Apherusa glacialis, Ischyrocerus anguipes and Onisimus spp. Individuals of these species grew significantly from May to July. Macrofaunal densities were highly variable among both samples and stations, and were not obviously related to distance from the ice edge after allowing for local habitat effects, including influences of ice type (increased densities in rough ice), meltwater (decreased densities) and pan ice (increased densities).

Key words: under-ice, ice edge, fast ice, Pond Inlet, ice microalgae, ice fauna, amphipods, chlorophyll, nutrients